Method of and apparatus for fractional distillation.



W. E. LUMMUS.

METHOD OF AND APPARATUS FOR FRACTION/XL DISTILLATION. APPLICATION FILED APR. 6,1916- 1 ,1 6,33%. Patented Feb. 20, 1917.

Z SHEETS-SHEET I. I

W. E. LUMIVIUS.

METHOD OF AND APPARATUS FOR FRACTIONAL DISTILLATION.

APPLICATION FILED APR. 6. 1916.

1,91 6 8%. A Patented Feb. 20, 1917.

2 SHEETS-SHEET 2.

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WALTER E. LUMMUS, OF LYNN, MASSACHUSETTS.

Application filed April 6, 1916.

- To all whom it may concern:

in the art to which it appertains to make and use the same.

This invention relates to distillation, and more particularly to an improved method of and apparatus for fractional distillation.

To obtain an eflicient and uniform selective condensation of the vapors in each of the reflux condensing chambers of a distillation column, it is necessary to maintain a relatively uniform temperature difference 1' between the cooling medium and the vapors to be affected along approximately the entire path of the circulation of the cooling medium. Heretofore attempts have been made to circulate the cooling medium through the chambers of a condensing column by means of a trombone coil which consisted of a series of pipes connected in parallel and formed into a trombone shape to give a long path for the circulation ofthe medium. The pipes of the trombone cooling,

coils were limited to a comparatively small cross-sectional area and in, order to have a sufficient volume of cooling medium to condense the vapors in more than one chamber, it required a high velocity of circulation. With a rapid circulation the condensation is greater so that, in the first few chambers there was an excess of condensation, which crfiited a deficit-of vapors in the first few chambers. The mechanical limitations of constructing the trombone coils do not permit a sufficient increase in the number of pipes in parallelto provide the requisite volume of cooling medium to give a proper temperature difference in all the chambers of the column. Also, the

larger the number of coils in paralleh'the' more non-uniform is the circulation of the cooling medium in the pipes. Under these conditions, the effect obtained by the circulation of the cooling medium in a trom- Specification of Letters Patent.

METHOD OF AND APPARATUS FOR FRACTIONAL DISTILLATION.

Patented FebQZfl, 1W1? Serial No. 89,272.

ture difference rapidly decreased as the medium circulated through the first few' condensing chambers, and practically disappeared in the succeeding chambers in which no condensation was obtained.

The primary object of the present inven tion is to provide an improved method of and apparatus for controlling the cooling medium of the condenser of a reflux distilling apparatus to obtain an eflicient fractional distillation.

In accordance with this object, one feature of the invention contemplates an improved system of distributingthe cooling medium in a distilling apparatus by which the cooling medium is circulated in a stream and the stream so disposed that the rate of absorption of heat by the medium will maintain a substantially and relatively uniform temperature difference between the cooling medium and the vapors in all of the chamtemplates the provision in a distilling ap-' paratus of a circulation system by which the cross-sectional area and the total length of the path of the stream in each condensing compartment can be varied to maintain a substantial temperature difference between the cooling medium and the vapors in all of the chambers under the peculiar conditions present.

In the preferred form of the invention,

the distilling column is provided with a series of reflux condensing chambers which are interchangeable so that any number of one standard type of chamber can be employed in building a column to obtain the required selective condensation. The chamber has a condensing compartment containing a definite number of condensing tubes. The cooling medium is circulated through these tubes in a stream which has a constant cross-sectional area equal to the sum of cross-sectional areas of the number of tubes. The stream flows in a path back and forth across the chamber while advancing from one side of the chamber to the other at right 7 angles to the direction of flow. The stream is guided back and forth through the tubes in advancing through the chamberby means of manifold plates which inclose the ends of the tubes and have partitioned guide chambers of area sufficient to cover the num ber of tubes which make up the cross-sectional area of the stream, or twice that number at the point of return.

All of the manifold plates are adapted to be secured to the tube sheets in the same manner, so by employing different sets of manifold plates having various arrangemerits .of guidechambers, with the same number of tubes, the path of the circulatl'is a side elevation of a fractional distillation apparatus embodying my improved invention; Fig. 2 is a horizontal section of one of the reflux condensing chambers taken on the line X of Fig. 1; Fig. 3 is a vertical section of the reflux condensing chamber taken on the line X of Fig. 2; Fig. 4 is a vertical section of the reflux condensing chamber taken on the line X of Fig. 3; Fig. .5 is a plan View of the manifold plate used with the reflux condensing chamber illustrated in Figs. 2, 3 and 4; and Figs. 6 and 7 are plan views of a set of manifold plates which may be used with the condensing chamber shown in Fig. 2 to secure a different distribution of the condenser cooling medium than the manifold plate illustrated in Fig. 5.

The apparatus illustrated in Fig. 1 is a periodic rectifying still for fractional distillation. When using this apparatus for the distillation of a solution mixture of methyl alcohol and water, for-example, the alcohol-water solution is placed in a boiler 10 where it is vaporized and the vapor is passed through a conduit 12 to a boiling section 14 of the distilling column. From the boiling section the vapor is passed up through the boiling cap sections 16 into the reflux condensing chamber 18. The vapor then passes through five succeeding reflux condenslng chambers 18 into a final condensing chamber 20 where the last traces of water vapor are condensed and alcohol vapor is conducted by a conduit 22 into a condenser 24 where the vapor is condensed and drawn off through the hydrometer reading reservoir or tail box 26. The alcohol- J water mixture, in passing through the boil ing compartment 14 and boiling cap chamber 16, is rapidly distilled so that the percentage of Water is greatly decreased and the boiling point of the mixtures in each section becomes gradually lowered. When the material reaches the first reflux condensing chamber the-mixture is generally of such a composition that the boiling point is comparatively close to the boiling point of alcohol, so that after passing through the six reflux condensing chambers 18 and the final chamber 20, the vapor passing through the compartment comes in contact with a condenser to aid in removing the water vapors. The cooling medium usually employed in the condensers is water, but other cooling liquids and gases may be employed. The cooling medium of the still shown' in the drawings enters the condenser 24 through a valve 28, passes up through the condenser 24. and out through a pipe 30 into the first condensing coil of the final condenser chamber 20. It is circulated through the two coils of the condenser 20 and passes in succession down through the cooling coils of the reflux condensing chambers 18 which are controlled for a continuous circulation by means of manifold connecting pipes 32, and then passes out through the valve 34.

The reflux condensing chamber illustrated in Figs. 2, 3 and 4 consists of an interchangeable unit section which has substantially the same construction as the unit section illustrated and described in my patent for a distilling apparatus No. 731,799, dated June 23, 1903. The condensing chamber has a rectangular shape with two sets of side walls 36 and 38 and a connecting flange 40 is secured around the periphery of the chamber at the top and bottom of the Walls. A boiling deck 42 is mounted within the top of the chamber, and on this deck are secured a series of boiling caps 44 and return pipes 46 which are substantially the same as those shown in my prior patent. \Vithin the chamber is mounted a pair of vapor circulating partitions 48 and 50 which divide the chamber into three compartments, a boiling compartment-52 into which the boiling caps of a lower compartment project, a condensing compartment 54 between the partitions, and a vapor compartment 56 between the partition 48 and the deck 42. The partitions 48 and 50 have a vapor-tight connection with the side walls 38 and only one of the side walls 36, so as to leave vapor passages 58 and 60, between the ends, to the partitions and the other side wall 36. By this constructionthe vapors passing up from the boiling compartment are forced to pass througlithe condensing compartment around condensing tubes 72 andup into the vapor compartment 56, where they pass through the boiling caps 44 and into the boiling compartment of the chamber above. A dam 64 is secured between the walls 38 and upon the partition 48 to form an overflow compartment for the solution coming down through the return pipes 46.

The cooling medium for condensation is circulated through the condensing tubes in a stream, which stream has a cross-sectional areaequal to the sum of the cross-sectional areas of a definite number of condensing tubes 72. This stream flows back and forth across the chamber, and has a path which advances across the chamber in a direction at right angles to the direction of flow. The vapor passing through the condensing compartment flows in a counter-current to the cooling medium and by uniformly distributing the tubes in the chamber all parts of the vapor aresubject to the same cooling action. The walls 38 of the condensing chamber have a rectangular opening 66 which is substantially coincident with the condensing compartment, and over these openings a tube sheet 68 is sweated to the walls 38 and secured in position by means of rivets 70. A series of condensing tubes 72 extend across the condensing compartment and have their ends secured in the tube sheets 68 and their ends open on the outside of the sheets. A set of manifold plates 74 for inclosing the ends of the tubes is secured to the tube sheets by means of bolts 76 and the'joints between the tube sheets and manifold lates are properly packed to give a liquid-tlght joint. The manifold plates illustrated in Figs. 2, 3 and 5 are provided with guiding chambers 78 and 80 which are adapted to give a path for the cooling medium which will cross the condensing chamber three times in passing through the tubes 72. The chambers 78 and 80 are separated by a partition 82 which is adapted to have a water-tight connection with the tube sheet to confine the. cooling liquid to a definite crosssection. Each chamber 80 has a pipe flange 84 to which the circulating pipes are connected. The flange 84 through which the cooling liquid enters is at the bottom of the manifold plate, and the flange 84 through which the cooling liquid discharges is at the top of the manifold plate to prevent trapping of air or gases in the tubes.

Asillustrated in Fig. 2 the cooling medium will enter through a circulating pipe 32, at the left, into a chamber 80, which incloses and directs the medium into the twelve,

tubes 7 2. The medium then passes through the tubes and into the chamber 78 on the right which has sufficient area to inclose twenty-four tubes so that the medium is directed back through twelve more tubes and passes into a chamber 78 on the lefti- The chamber 78 on the left has an area sufiicient to inclose twenty-four tubes and directs the medium back through twelve more tubes where it flows to chamber 80 on the right and cross-sectional area sutlicient to direct the cir- -culat1ng medium through twelve tubes, and

the partitions 94 which separate these chambers are adapted to make a liquid-tight connection with the tube sheet. The plate 88 has three chambers 92 which have an area suflicient to direct the cooling medium into twelve of the cooling tubes, and the partitions 94, are adapted to have a liquid-tight connection with the tube sheets. Vith this construction it will be noted that the pipe flanges 84 in the chambers 90 of the plate 86 will both be on the same side of the condensingchamber, which differs from the construction illustrated in Figs. 1, '2, 3 and 4,

in which'the connecting pipes 32 have a connection on the opposite sides of the condensing chamber. In using the plates 86 and 88, therefore, the connecting pipes 32 will all be on one side of the condensing chamber. The flanges 98 and 100 of the plates'86 and 88 are of the same size as the flange 102 of the manifold plate 74, and the opening in the flanges of the plates 86 and 88 for the fastening bolts 76 coincide with the openings in the flange of the manifold plate 74 so that they can be used interchangeably.

The manifold plates illustrated inFigs. 5, 6 and 7 show forms of'plates by which two different characters of distribution of a cool.- ing medium can be obtained through the circulating tubes 72. It will be obvious also that if manifold plates wereused, having only one guiding chamber, the liquid would only cross the chamber once in passing through the tubes 72, and by using 36 tubes, as shown in Fig. 4. a distribution could be secured in which the path of a circulating liquid would cross the chamber one, two, three, six and nine times in passing through the tubes 72. Further, the arrangement of the'tubes and guiding chambers could be manipulated to secure any desired distribution of the cooling medium. This form of construction is especially advantageous since condensing chambers of one standard of construction can be made and the tubes permanently inserted. and, by employing manifold plates having different numbers of guiding chambers, the path of the cooling medium can be greatly changed.

While condensing vapors in the-condensing compartment, a large number of factors have to be taken care of. The differthe transfer ofheat; the volume of cooling.

medium in the stream influences the transfer of heat; the length of the stream in conof the condensing chamber, a very large tact with the vapor influences the transfer of heat; the velocity of the flow of the stream influences the transfer of heat; the extent of tube surface in contact with the vapor influences the transfer of heat; and the velocity offlow of the vapor in the chamber in-' fluences the transfer of heat. With applicants mproved system of distribution of the cooling medium all of these factors are provided for and can be easily controlled.

'Thevolume of vapor passing throughthe condenser can be controlled by the size of the condensing chamber which is designed to have a capacity for a predetermined volume of liquor. The velocity of flow -of the vapors through the chamber to get the proper condensation in' each chamber, as well as a proper distribution of vapor in all of the chambers, is controlled by the n'llme ber of tubes in the condensing compartment. The number of tubes in the compartment also controls the extent of tube surface in contact with thevapor. With tubes connected between tube sheets at opposite sides number of tubes can be uniformly distributed in the chamber and obtain any desired condensing area. The tubes can be placed close together to constrict the vapor passage, and thus increase the velocity of the vapor. The use of a predetermined" number of tubes and the appropriate forms of manifold plates as explained above, will control the temperature difference between the cooling medium and the vapor, the volume or cross-sectional area of the stream, the velocity of flow and the length of the stream. By balancing the factors mentioned 'above, a relatively uniform temperature difference between the'cooling medium and vapors to be condensed can be maintained in all of the chambers to obtain the full condensing effect in each chamber. The temperature of the in-flowing water can be maintained substantially constant, and by treating material having vapors with definite boiling points the temperatures in each chamber can be very delicately controlled to get a selective condensation in; each chamber. In practice, it has been found that temperature differences between the vapors and cooling medium of from 10 to 20 F. give excellent results. When using circulating tubes of high heat conductivity it is possible to maintain a very minute temperature difference between the vapors and cooling medium.

The improved method of manipulating the condensing chambers further increases the capacity of the still many fold, due to return pipes. The flexibility of the sys-.

tem in changing the distribution of cooling medium permits the maintenance of slight differences of temperature between the cooling medium in succeeding chambers to provide for the slight changes ofboiling point of the mixtures in those chambers.

In the apparatus described, a construction is shown in which copper is used exclusively, and the drawings are merely diagrammatic and do not attempt to show the packings and joints to make vapor-tight andliquid-tight joints. It is to be understood that, where different metals are used in the construction, such as the use of cast-iron and copper or steel, cast-iron and copper, etc., the usual expansion packing joints will be employed. Further, I do not limit myself to the use of the condensing chamber in a periodic still, since it may be used in practically any type of still, periodic or continuous, and the number of chambers will be modified to provide" for the character of material to be treated.

Having thus described the nature of my invention and set forth a preferred form of construction embodying the same, what I claim as new is:

1. The method of obtaining selective condensation in a distilling apparatus of the column type comprising, vaporizing a solution'mixture, passing the vapors successively through a series of reflux condensing chambers, circulating a cooling medium in a stream through the condensing chambers in the path of the vapors, and controlling the area and length of the stream in the chambers so that the rate of absorption of heat by the medium will give a substantially constant temperature diflerence between the cooling medium and the vapors throughout all the chambers regardless of the volume of vapors being distilled.

2. The method of obtaining selective condensation in a distilling apparatus of the column type comprising, vaporizing a solution mixture, passing the vapors successively through a series of reflux condensing chambers, conducting condensing medium in a stream through the condensing chambers,

4 and varying the length of path and the areation mixture, passing the vapors successively through a series of reflux condensing chambers, circulating condensing medium in a stream through the condensing chambers, and controlling the area, length and velocity of the stream in the chambers to provide a relatively constant temperature difference between the water and the vapors in all of the chambers.

4c. The method of obtaining a condensation in a distilling apparatus of the column type comprising, vaporizing a solution mixture, passing the vapors successively through a series of reflux condensing chambers, circulating a cooling medium in a stream through the condensing chambers, and controlling the cross-sectional area of the stream the length of path of the stream the rate of flow of the stream and regulating the velocity of flow of the vapors in the chambers so that the rate of absorption of heat by the medium will result in a substantial temperature difference between the cooling medium and the vapors in all of the chambers, to obtain a full condensing effect in each chamber.

5. The method of obtaining a selective condensation in a distilling apparatus of the column type comprising, vaporizing a solu in combination, reflux mounted on the tube sheets tion mixture, passing the through a series of reflux condensing chambers, conducting a cooling medium in a stream through the condensing chambers. and controlling the cross-sectional area of the stream, the distribution of the stream, the velocity of the vapors and extent of cooling surface in contact with the vapors, to maintain a substantial temperature difference between the cooling medium and the Vapors in all of the chambers.

6. A reflux condensing apparatus having, condensing chambers mounted one above the other, a series of condensing pipes in the chambers'which are connected between tube sheets, manifold plates over the ends of the tubes for controlling the length of path of the cooling medium transversely ,of the chambers, and means for connecting the manifolds of all of the chambers to obtain a circulation of the cooling medium.

7. A reflux condensing apparatus having, in combination, reflux condensing chambers connected in series, a series of condensing pipes in the chambers which are connected between tube sheets, a series of manifold vapor successively plates inclosing the ends of the tubes having partitions arranged transversely of the plates to contact the tube sheets for controlling the length of path of the cooling medium in each chamber, and means for connecting the manifold plates of all the chambers to distribute the cooling medium from one chamber to the next.

8. A reflux condensing apparatus having, in combination, reflux condensing chambers connected in series, a plurality of condensing tubes in the chambers which are connected between tube sheets, and a pair of manifold plates for inclosing the ends of the tubes of each chamber, the manifold plates of the different chambers having a different number of partitions for varying the path of flow of the cooling medium in the different chambers.

9. A reflux condensing apparatus having, in combination, a boiling chamber, a series of cooling tubes connected between tube sheets at two sides of the chamber, and a series of sets'of interchangeable manifold plates for inclosing the ends of the tubes, each set of plates having partitions to form guiding chambers for the ends of the tubes to obtain different distributions of the cooling medium through the tubes.

10. A reflux condensing apparatus having, in combination, a series of interchangeable unit reflux condensing chambers adapted to be connected in series, a plurality of circulating tubes in the chambers which are connected between tube sheets, and manifold plates for inclosing theends of the tubes of each chamber, the manifold plates of the different chambers having a different number of partitions for varying the flow of the cooling medium in the different chambers.

11. A reflux condensing apparatus having, in combination, a series of interchangeable unit reflux condensing chambers adapted to be connected in series, a plurality of condensing tubes mounted in the chambers with their ends passing through tube sheets located on opposite sides of the chamber, and

a series of sets of interchangeable manifold I the tubes.

WALTER E. LUMMU S. 

